DUMMERSTON — Vermont State Police are investigating how a transient man obtained a firearm he cannot legally possess.

Robert Taylor Brewer, 64, was pulled over by State Police on Monday during a traffic stop on Interstate 91 in Dummerston. Police said they conducted a search and found a .40-caliber handgun in Brewer’s car.

Brewer had a prior conviction of domestic assault, which, under federal law, prohibits him from possessing a firearm. Although he was not arrested, State Police said they seized the firearm and the investigation is still ongoing.